[RFI] RFI from Ariss cable modem

Chuck af4o at arrl.net
Sat Jul 6 18:46:17 EDT 2013

> Have not been very active at home in months although doing quite a bit
> of outdoor qrp hf. Decided to go all qrp hf at home and sell off 100w
> gear. Just wasn't using it.
> Anyway, setup the FT817, BLT (tuner), ANC-4 and ladder line fed delta
> loop. All solar power with a 35ah gel and solar panel.
> Then noticed i had about s8 constant noise with the ANC-4 off on 20
> meters and other bands of varying intensity also. Pulled the breaker to
> the house, gone. Then narrowed it down to a 
> individual breaker. Then to the adapter for the exercise bike (in the
> room with the radio gear) and the cable internet/telephone/wireless
> modem (an Ariss brand). Just unplugged the bike 
> adapter will deal with it later.
> On the Ariss, tried unhooking each of the four CAT5 cables, the cable
> coming in, and the telephone line, no luck. Tried putting toroids on the
> ac line, no luck. Tried a APC UPS i had. Some
> reduction, maybe down to s6. Built a ac line filter (brute force), GFCI
> on the line tripped. A commercial made brute force ac line filter may
> help but i doubt totally. 
> Just about ready to call the cable company and ask for another brand
> modem, then got desperate and  wrapped the unit in aluminum foil and
> noticed when i touched the foil to the shield
> on the cable plug, noise was gone. Went to wally world and got a 94 cent
> aluminum baking pan. Sit the modem in the pan and covered the top with
> aluminum foil. Just wrapped the foil around
> the cables rather loosely touching the foil to the cable shield again.
> Left a couple of corners of foil loose to give the modem air. Noise
> gone.
> After more testing i am going to neaten things up by drilling air holes
> in the pan and cover with foil again. Then fashion some braided line
> soldered to the pan and clamp to the cable shield. 
> That should do it. Oh i let the wireless antenna poke out the corner.
> Didn't affect the noise thank goodness.
> Hope this may help someone with one of these beasts or similar. Oh the
> Ariss is about 6' from the FT817 and ladder line. The bike adapter even
> closer.
> 73
> Chuck
> AF4O

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